Which one of the following equations of motion represents simple harmonic motion ?

where k, k₀, k₁ and a are all positive.

Each of the two strings of length 51.6 cm and 49.1 cm are tensioned separately by 20 N force. Mass per unit length of both the strings is same and equal to 1 g/m. When both the strings vibrate simultaneously the number of beats is

A wave in a string has an amplitude of 2 cm. The wave travels in the +ve direction of x axis with a speed of 128 m/s. and it is noted that 5 complete waves fit in 4m length of the string. The equation describing the wave is

Three concentric spherical shells have radii a, b and c (a < b < c) anf have surface charge densities $$\sigma $$, $$-$$$$\sigma $$ and $$\sigma $$ respectively. If V_A, V_B and V_C denote the potentials of the three shells, then, for c = a + b, we have